All evaluations have been completed for the study. Results show that both RIF and RBT resulted in significant reductions from baseline in mean EE2 area under the plasma concentration time curve (AUC) values. AUC's of NE also significantly decreased following RIF and RBT administrations. Maximum plasma concentrations (Cmax) of EE2 decreased significantly following RIF but not RBT administration. Cmax's of NE did not change significantly. When compared, RIF resulted in a significantly greater median percent decrease in the AUC's of both EE2 and NE (p's <0.05) and the Cmax's of EE2 (p < 0.05) than RBT. RIF resulted in a median percent increase of 38.9 [92.7] % in follicle stimulating hormone values suggesting a trend toward less suppression of the pituatary-gonadal axis. In spite of this finding, suppression of ovulation occurred in all subjects after taking RIF or RBT; plasma progesterone levels were less then 1.0 ng/ml in all subjects on day 21. The results of this study will be used by the FDA in consideration of amendments to the package labelling of RBT.